Editorial: Colyn Crane-Robinson (1935–2023)

Scientific colleagues and close friends were saddened to learn about the death of Colyn Crane-Robinson (Figure 1 ), who died on 5 March 2023. From a lifetime of enthusiastically and gregariously applied dedication, Colyn Crane-Robinson made substantial contributions to our understanding of nucleic acid structures and DNA–pr otein interactions. Numer ous mechanistic insights were due to his ability to de v elop, adapt and improv e e xisting methodologies, such as that of chromatin immunoprecipita tion. Such innova ti v e science resulted in many publications, including several landmark papers published in Nucleic Acids Research ( 1–13 ). Much of his work was pioneering and often highly collaborati v e, and it re v ealed une xpected truths by shedding new light on underlying principles. Colyn Crane-Robinson was born

polymer company), but soon afterwards its r esear ch division was closed forcing him to move on to Portsmouth Polytechnic (now Uni v ersity of Portsmouth). Crane-Robinson joined in 1963 as a Lecturer, later becoming a Pr ofessor, before Pr ofessor Emeritus upon his r etir ement in 2000.
At Portsmouth, much in collaboration with Morton Bradbury and Henry W. Rattle (one of Crane-Robinson's first PhD students), he initially used nuclear magnetic resonance to investigate the dynamic folding of peptides and proteins, such as helix-coil transitions, resulting in a string of high profile publications (14)(15)(16)(17)(18). Similar analyses were then successfully applied to histones, some of the most conserved cellular proteins, pivotal for packaging the nuclear genome (19)(20)(21). This work underpinned Crane-Robinson's future dri v e to better understand histone-DNA interactions, chromatin and the role of histone modifications and histone variants in gene regulation. Early highlights of this histone-DNA work include the structural analysis of histone H1-nucleosome interactions, especially on the location of histone H1 on the nucleosome (22)(23)(24)(25). Another important study centred around characterisation of the H3 / H4 nucleosomal kernel as a fundamental chromatin unit, published in Nucleic Acids Research ( 1 ). Crane-Robinson's group also studied another important class of chromatin proteins -those that contain HMG-boxes. This work led to the solution structure of a HMG-box (4) which re v ealed a conserved DNA-binding (and bending) motif found in various chromatin and transcription factors, such as the sex-determining factor, SRY. The work on HMG-box containing proteins also led to the analysis (with Peter Privalov) of the thermodynamics of the HMG-box protein interaction with DNA ( 8 , 26 , 27 ).
Although Crane-Robinson interacted with laboratories around the world, his most widely recognised scientific contribution was from a 'home grown' project, initiated and performed solely in 'his' Biophysics Unit at the Uni v ersity of Portsmouth. Here, together with his PhD student Tim Hebbes, he de v eloped nati v e chroma tin immunoprecipita tion, where antibodies recognizing modified histones are used to enrich specific regions of the genome. This technique, and its later deri vati v es, such as ChIP-seq (chromatin immunoprecipitation sequencing) have been invaluable in making functional connections between histone modifications and DN A processes, particularl y gene expression ( 3 , 28-32 ). Chromatin immunoprecipitation has now become a mainstay for analysing epigenomes, helping us to understand the functional genome. In this way, it contributes to our understanding of cell type, cellular function and gene regulation mechanisms in health and disease. Indeed, Crane-Robinson recognized this contribution; in his own words, he claimed to be 'the principal midwife' at the birth of chromatin immunoprecipitation ( 33 ).
Chroma tin immunoprecipita tion remains an in valuable technique f or the modern in vestigator. For instance, it is used to help identify chromatin features that characterise or define particular regulatory DNA elements, such as enhancers and promoters. Crane-Robinson contributed to this quite early on with two subsequent studies published in Nucleic Acids Research . The first paper highlights acetylation of histone variant H2A.Z as a hallmark of the promoter proximal region and 5 end Nucleic Acids Research, 2023, Vol. 51, No. 15 7711 of acti v e genes, while the unacetylated form is depleted from both acti v e and inacti v e genes ( 10 ). The second paper showed that de v elopmental acti vation of a paradigm gene (the lysozyme gene) in chicken macrophage cells is linked to core histone acetyla tion a t its enhancer elements ( 11 ), connecting histone acetyla tion and enhancer function.
Crane-Robinson was not someone to rest on his laurels, and he continued to push forward right up to and including the last few weeks of his life. Indeed, it is a testament to his dedication that he continued to contribute very original and fundamental work in the decades following his formal r etir ement in 2000. Most of his latest papers, all in collaboration with Peter Privlov, examined the forces maintaining the DNA double helix and protein folding and the role of hydration and enthalpy versus entropy-dri v en processes in this context. Pri valov, an e xperimentalist, de v eloped differential scanning calorimetry (DSC) to measure the thermodynamic principles of protein and nucleic acid folding ( 34 ). Cr ane-Robinson collabor ated with Privalov from the early 1980s and he described their relationship as one of an apprentice (him) and master (Pri valov). Howe v er, to most colleagues familiar with the situation, it was clear that their interaction was m utuall y beneficial. This synergy propelled the two of them to fruitfully explore the interactions between DNA and transcription factor DNA binding domains (DBDs).
With regards to DNA duplex thermodynamics, their findings challenged the generally held view that G-C base pairs stabilise duplex es mor e than A-T base pairs because they possess an additional Hydrogen-bond (three versus two). These findings are summarised in their last paper, published in 2022 ( 35 ), which built on work published over the last few years, ( 13 , 36 , 37 ).
A key study in this string was the Vaitiekunas et al. paper ( 13 ), published in Nucleic Acids Researc h , w here calorimetric experiments measuring the energetics of DNA duplex formation led to the provocati v e proposal that the intrinsic enthalpies of G-C and A-T base pairs are very similar. An A-T base pair gains this extra enthalpic stabilisation from one or two water molecules that are strongly fixed by its polar groups in the minor groove. So, where does the apparent overall stabilizing effect of G-C base pairs stem from? As with all enthalp y / entrop y trade-offs, it must be in the entr opy. They pr opose that on melting (breaking) an A-T base pair, the immobilised water is released, and it gains a large amount of favourable translational entropy in the process, accounting for the difference. It is astonishing to see how carefully planned and executed thermodynamic analysis of DNA melting can provide such fundamental insights nearly 70 years after the structure of DNA was solved.
Privalov, Cr ane-Robinson and collabor ators also challenged the previously held belief that DNA energetics ar e temperatur eindependent. Using car eful measur ements with se v eral short duple xes, they showed this is not the case, with the hydrating water once again playing a critical role ( 13 , 38 ). Interestingly, they also showed that similar conclusions can be drawn about the principles of alpha-helices folding in proteins (36).
Crane-Robinson ne v er really stopped being scientifically acti v e and he was in the lab until the very end. Indeed, we had stimulating discussions with him just a few weeks before his death. He was a fascinating, original personality, yet strikingly humble in the face of science. He was a great mentor and generous with insights and thoughts. He was witty with remarks, anecdotes and sometimes flamboyant in his dress style, often being the first and 'best' dressed person on the dance floor at conference parties.
He simply refused to retire and continued to walk through the wonderland of scientific discovery until the very end. Crane-Robinson not only gained pleasure from fruitful collaborations and intense discussions, but he considered them critical for scientific progress. He wrote: 'Science is a conversation: its participants tell each other about their results, and the building rises from their combined efforts' ( 34 ). We will miss this conversation with him.